I'm working on a Diner that neither both the Ramp Down 02A and Babs Flash 02C work. I'm also having an additional strange issue with solenoid 07A Knocker that when activated in the diagnostics it stays locked on even if you shut the machine off and then back on. If you let it sit for a while maybe it will reset and not be locked on. I read that U10 PIA controls sounds and solenoids drives. Looking at the schematics, I just don't see what controls transistors Q22,23,2425,30,31,32&33. I just see where the 74LS374 at U28 has something to do with "driving" these transistors.

I just can't figure it out, any advice would be greatly appreciated.

Thank

Rick

Grumpy, what do you advise? I did install my Leon Test Rom in U27 and checked the outputs of the PIA's pins 2-17 and all that were supposed to where toggling between 0 and 5 volts. I realize not all do this, there's a couple of exceptions like U38. I'd be interested to hear what you advise?
Thanks

I will try this and report back.
Thanks!

Logic tester in hand and here's what I found:

Game Rom installed, Solenoid diagnostics enabled and set "manually" to test 2A Ramp Down. The result is that U20 pin 13 is high. Pin 12 of U20 is low and pulses high, U20 pin 11 pulses high and same pulsing high at the base of Q21.

Hopefully this helps. Anything else I need to check please let me know and I"ll report back with the results.

On the base of Q25 with solenoid test 2A running I get a low with high pulses. When I check pin 3 of 1J11 I get a high.

Turns out Q25 was defective. I replaced it with a TIP102 and we're back up and running again. I still need to check why the knocker appeared to be locking on but will report back with what I found.
Thanks Grumpy for the advice and guidance. Very much appreciated!

Update on the knocker being locked on. Turns out the coil wrapper at the very bottom had the windings ever so slightly exposed. One of the windings was protruding a bit past the actual body and if you look really closely it was burnt right where it came in contact with the back plane that's obviously grounded. So turn the game on and the coil was grounded with power to it and it fired and stayed on until it took out the fuse or power quickly shut back off. The connector to the knocker was disconnected when I got the game, I incorrectly assumed it was because someone didn't want the "noise".

Thanks for all the help Grumpy. Now onto getting it shopped and looking/playing great.